On Twitter, a fan asked "Game of Thrones" actress Lena Headey if she ever feels insecure.

Headey then responded with an open thread about her struggles with anxiety and depression.

Mental illnesses are indiscriminate. They can strike anybody at any time. Actress Lena Headey, who currently stars as Cersei Lannister on "Game of Thrones," drove this point home in a candid Twitter thread about anxiety and depression.

On Thursday, a Twitter user asked Headey if she ever struggles with insecurity.

Surprisingly, the 43-year-old responded to the tweeter — and dropped some tools she's used to cope with anxiety and depression.

There's a real reason why Headey's vulnerability is resonating with thousands of people on Twitter.

Anxiety and depression are two of the leading mental illnesses in the US. Anxiety disorders are the most common mental illness in America, according to the National Institute of Mental Health. About 40 million Americans, or 18% of the US population, has an anxiety disorder.